Focus ring for a plasma-based semiconductor processing tool

Abstract

A focus ring for a plasma-based semiconductor processing tool is designed to provide and/or ensure etch rate uniformity across a wafer during a plasma etch process. The focus ring may include an angled inner wall that is angled away from a center of the focus ring to direct a plasma toward the wafer. The angle of the angled inner wall may be greater than approximately 130 degrees relative to the top surface of the wafer and/or may be less than approximately 50 degrees relative to an adjacent lower surface of the focus ring to reduce and/or eliminate areas of overlapping plasma on the wafer (which would otherwise cause non-uniform etch rates). Moreover, an inner diameter may be configured to be in a range of approximately 209 millimeters to 214 millimeters to further reduce and/or eliminate areas of overlapping plasma on the wafer. In this way, the focus ring provides and/or increases etch rate uniformity across the wafer, which may reduce structural variations across semiconductor devices being formed on the wafer and/or may increase processing yield.

What is claimed is: 
     
         1 . A method, comprising:
 forming a bottom surface of a plasma focus ring;   forming a lower surface of the plasma focus ring above the bottom surface such that an inner diameter of the plasma focus ring is in a range of approximately 209 millimeters to approximately 214 millimeters; and   forming an angled inner wall of the plasma focus ring above the bottom surface and adjacent to the lower surface such that the angled inner wall is angled away from a center of the plasma focus ring at an angle less than 50 degrees relative to the lower surface.   
     
     
         2 . The method of  claim 1 , further comprising:
 forming a top surface of the plasma focus ring above and connected to the angled inner wall; and   forming an outer wall of the plasma focus ring connected to the top surface and the bottom surface.   
     
     
         3 . The method of  claim 2 , wherein forming the top surface comprises:
 forming the top surface to a width of less than approximately 10 millimeters.   
     
     
         4 . The method of  claim 2 , wherein the outer wall comprises a portion that is angled inwardly toward the angled inner wall and the center of the plasma focus ring. 
     
     
         5 . The method of  claim 2 , wherein the top surface is curved, round, or semi-circular. 
     
     
         6 . The method of  claim 2 , wherein the bottom surface connects, and is orthogonal, to at least a portion of the outer wall. 
     
     
         7 . A method, comprising:
 forming a bottom surface of a focus ring;   forming a lower surface of the focus ring above the bottom surface and adjacent to an open center of the focus ring; and   forming an angled inner wall of the focus ring above the bottom surface and adjacent to the lower surface such that the angled inner wall is structured to direct or redirect plasm to the open center of the focus ring.   
     
     
         8 . The method of  claim 7 , wherein the angled inner wall is angled away from the open center of the focus ring at a uniform angle along a circumference of the focus ring. 
     
     
         9 . The method of  claim 7 , wherein the angled inner wall defines the open center of the focus ring. 
     
     
         10 . The method of  claim 7 , wherein the angled inner wall is above the lower surface. 
     
     
         11 . The method of  claim 7 , wherein the angled inner wall connects to the lower surface. 
     
     
         12 . The method of  claim 7 , further comprising:
 forming an outer wall of the focus ring connected to the bottom surface.   
     
     
         13 . The method of  claim 12 ,
 forming a top surface of the focus ring above and connected to the angled inner wall and the outer wall.   
     
     
         14 . The method of  claim 12 , wherein a height of the outer wall is greater than a height of the angled inner wall. 
     
     
         15 . A method, comprising:
 forming a bottom surface of a plasma focus ring;   forming a lower surface of the plasma focus ring above the bottom surface;   forming an angled inner wall of the plasma focus ring above the bottom surface and adjacent to the lower surface; and   forming an outer wall of the plasma focus ring above the bottom surface and connected to the angled inner wall.   
     
     
         16 . The method of  claim 15 , wherein the angled inner wall is connected to the lower surface. 
     
     
         17 . The method of  claim 15 , wherein the outer wall comprises at least one of an angled portion or a straight portion. 
     
     
         18 . The method of  claim 17 , wherein the outer wall comprises the angled portion and the straight portion. 
     
     
         19 . The method of  claim 18 , wherein the lower surface corresponds to an intersection of the angled portion and the straight portion of the outer wall. 
     
     
         20 . The method of  claim 18 , further comprising:
 forming a top surface of the plasma focus ring connecting the angled portion of the outer wall and the angled inner wall.